Vertically starting and landing airplane

ABSTRACT

A vertically starting and landing airplane with pivotable propellers in front and behind the center of gravity of the airplane, in which the propellers located in front of the center of gravity of the airplane have a greater number of blades than the propellers located behind the center of gravity of the airplane.

United States Patent [72] Inventors Siegfried Gunter deceased. late of Munich by [5 l Int. Cl B64c 27/28 Ruth Guenter. Executrix. Munich. [50] Field of Search 244/ 7. 49. Germany 65. 66

[2l Appl. No. 870,207

[22] Filed July 24, 1969 1 References Cited [45] Patented May 11, 1971 UNITED STATES PATENTS [73] Assignee Vereinigte Flugtec ni welke 3.037.721 6/1962 Stefanutti 244/ 7 ksellsfhafl f! beschrank" mung 3181.810 5/1965 Olson 244/7 W nugleugbau/Focke- 3,298,633 1/1967 Dastoli et al 244/700 Wulf/Hemkel-Flugzeugbau Bremen Germany Primary Exammer-M1lton Buchler 32 p i July 29 19 8 Assistant Examiner-Carl A. Rutledge 33 G Attorney-Walter Becker [54] I VERTICALLY STARTING AND LANDING AIRPLANE 3 Claims, 3 Drawing Figs.

[52] US. Cl 244/7 ABSTRACT: A vertically starting and landing airplane with pivotable propellers in front and behind the center of gravity of the airplane, in which the propellers located in front of the center of gravity of the airplane have a greater number of blades than the propellers located behind the center of gravity of the airplane.

. 1 vErrnc LLv' STARTING ANDLANDING AIRPLANE The present invention relates to a vertically starting and landing airplane with pivotable propellers located in front of and behind the center of gravity of the airplane, in which all of the blades of said propellers are identical.

With the heretofore known design of the above-mentioned type of airplane, the same number of blades is used for the pivotable propellers located in front and behind the center of the airplane. The requirements for equilibrium about the transverse axis makes it necessary that during a hovering flight, the center of gravity and the thrust center point of the airplane overlap or cover each other. During a horizontal flight, the center of gravity of the airplane must be located closer to the front propellers in order to assure stability of the airplane. In order to meet both requirements, it is necessary that the lift thrust of the front propellers is considerably greater than that of the rear propellers. Consequently, it would be necessary that the front propellers, in order to furnish a greater thrust than the rear propellers, work with a greater angle of incidence of the blade and thus with a higher lift coefficient. Each lift coefficient C A has inherent thereto a corresponding coefficient of resistance C The ratio of lift coefficient to resistance coefficient C /C is called profile gliding coefficient and determines the degree of efficiency of the propeller. The best profile gliding coefiicient has associated therewith an optimum lift coefficient. with an arrangement and design of the propellers according to the prior art as shown in FIG. 1, it is impossible that the front as well as the rear propellers will be able to operate at an optimum lift coefficient C. The deviation from the optimum results in a loss in the lift thrust which in turn decreases the obtainable max imum lift thrust total of all air propellers.

In view of the requirements for stability and equilibrium,

It is, therefore, an object of the present invention to provide an arrangement which will make it possible to operate all air propellers at an optimum lift coefficient C, so as to assure a maximum possible lift thrust total.

This object and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing, in which:

FIG. 1 is a top view of a prior art vertically starting and landing airplane in which the air propellers have identical blades and have an identical number of blades; I

FIG. 2 shows a vertically starting and landing airplane according to the invention in side view with pivotable air propellers located in front and behind the center of gravity of the airplane;

FIG. 3 shows in top view the design according to the invention of air propellers in front and behind the center of gravity.

The above outlined objectsand advantages have been realized according to the invention by so designing the air propellers that the air propellers in front of the center of gravity of the airplane will with preferably the same speed of rotation have a higher number of blades than those air propellers located behind the center of gravity of the airplane. The respective pivotable air propellers located in frontand behind the center of gravity may when in position for cruising be located approximately in the same alignment.

Referring now to the drawing in detail, and FIG. 1 thereof illustrating the prior art arrangement, it will be noted that according to FIG. 1 in which the front air screws 3 have the same number of blades as the rear air screws 4, the necessary increase in the lift thrust of the front air propellers 3 is obtained by a greater angle of incidence of the blades.

In view of the required stability and equilibrium, the front and rear air propellers cannot work simultaneously at the optimum lift coefficient C The deviation from the optimum brings about a loss in the lift thrust which reduces the maximum lift thrust total of all air propellers.

If the entire surface of the air propellers is in conformity with the different lift thrusts distributed unevenly over front and rear air propellers, all air propellers may be operated at an optimum coefficient C and may realize the maximum possib e lift thrust total. If, w en unevenly drstrlbuted, the total surface of all air screws is not changed, also the friction losses, as well as the degree of efficiency in fast flight will remain unchanged.

The requirement for a simple mass production of identical blades for the front and rear end propeller, the conditions of stability and equilibrium about the transverse axis of the plane, and the provision of a maximum lift thrust is, in conformity with the present invention, realized by the factthat the front air screw has a greater number of blades than the rear air screw as is shown for instance in FIG. 3.

It is, of course, to be understood that the present invention is, by no means, limited to the particular construction shown in the drawing but also comprises any modifications within the scope of the appended claims.

I claim:

1. A vertically starting and landing airplane with pivotable propellers located ahead of and behind the center of gravity of the airplane, in which all of said propellers have substantially identical-propeller blades, and in which the propellers located ahead of the center of gravity of the air plane have a greater number of propeller blades than the propellers located behind .the center of gravity of the airplane.

2. An airplane according to claim 1, in which the pivotable propellers ahead of and behind the center of gravity of the airplane are at cruising speed in substantial alignment with each other.

3. An airplane according to claim I, in which the propellers ahead of and behind the center of gravity of the airplane have substantially identical speed. 

1. A vertically starting and landing airplane with pivotable propellers located ahead of and behind the center of gravity of the airplane, in which all of said propellers have substantially identical propeller blades, and in which the propellers located ahead of the center of gravity of the air plane have a greater number of propeller blades than the propellers located behind the center of gravity of the airplane.
 2. An airplane according to claim 1, in which the pivotable propellers ahead of and behind the center of gravity of the airplane are at cruising speed in substantial alignment with each other.
 3. An airplane according to claim 1, in which the propellers ahead of and behind the center of gravity of the airplane have substantially identical speed. 